Actually, make the change to hash opt-in, rather than opt-out. It's a bit late to introduce a breaking change.

[SVN r64007]

hash/test/Jamfile.v2

@@ -7,6 +7,7 @@ import testing ;
 
 project hash-tests
     : requirements
+        <define>BOOST_HASH_NO_IMPLICIT_CASTS
         <warnings>all
         <toolset>intel:<warnings>on
         <toolset>intel:<cxxflags>-strict-ansi